Frequency selective gyromagnetic diplexer for coupling two lines, each having individual frequency, with a common line



0, 1963 J. BROWN, JR.. ETAL 3,101,456

FREQUENCY SELECTIVE GYROMAGNETIC DIPLEXER FOR COUPLING TWO LINES, EACH HAVING INDIVIDUAL FREQUENCY, WITH A COMMON LINE Filed Dec. 14, 1961 2 Sheets-Sheet 1 FIG.3.\ EA} INVENTORS JUL/AN BROWN JR. B JOHN G CLARK ATTORNEY 20, 1953 J. BROWN, JR.. ETAL 3,101,456

FREQUENCY SELECTIVE GYROMAGNETIC DIPLEXER FOR COUPLING TWO LINES, EACH HAVING INDIVIDUAL FREQUENCY, WITH A COMMON LINE Filed Dec. 14, 1961 2 Sheets-Sheet 2 FREQUENCY ABOVE RESONANCE 2 F I G. 5. 5 6.00-- 3 d I FREQUENCY BELOW RESONANCE d e f I i I I 0 s00 1000 1500 2000 4 11 M (GAUSS) FREQUENCIES BELOW RESONANCE '03 3 FIG.6. I FREQUENCIES ABOVE RESONANCE 1 0 500 1000 15'00 2000 INVENTORS 4 Fl MS (GAUSS) JUL/AN BROWN JR.

BYJOHN G. CLARK A JOR/VEY 7 United States Patent U FREQUENCY SELECTIVE GYROMAGNETIC DI- PLEXER FOR COUPLING TWO LINES, EACH HAVING INDIVIDUAL FREQUENCY, WITH A COMMQN LINE Julian Brown, J12, and John G. Clark, Clearwater, Fla, assignors to Sperry Rand Corporation, Great Neck, N.Y., a corporation of Delaware Filed Dec. 14, 1961, Ser. No. 159,222 3 Claims. (Cl. 3331.1)

The present invention relates to small and compact apparatus for diplexing electromagnetic waves of diiferent frequencies.

A diplexer is a familiar device that operates to separate into two ditferent channels electromagnetic waves of two different frequencies that are available together in one waveguide channel, or to couple into the same waveguide channel electroma-gnetic waves of two different frequencies which are separately available in respective waveguide channels.

It is an object of the present invention to provide a simple and compact diplexer for electromagnetic waves.

It is another object of this invention to provide a small, symmetrical Y-junction diplexer.

A further object of this invention is to utilize the properties of a gyromagnetic material in a Y-junction microwave device for diplexing electromagnetic waves of two ditferent frequencies.

These and other objects and advantages of the present invention will bemore apparent from the following description and claims, taken together with the accompanying drawings in which:

FIG. 1 is atop view of a diplexer of the present invention;

FIG. 2 is a partial sectional view taken at section IIII of FIG. 1;

FIGS. 3 and 4 are diagrams used in describing the diplexing operation of the device of this invention; and

FIGS. 5 and 6 are graphs used to help explain the method of obtaining the proper gyromagnetic material, field strength of the unidirectional magnetic field and frequencies to achieve diplexing operation in the device of FIGS. 1 and 2.

Referring now in detail to FIGS. 1 and 2, which illustrate the embodiment of the present invention for diplexing TEM mode waves, the device is comprised of an outer housing member 11 of non-magnetic material such as aluminum. Housing member 11 has a central aperture 12 extending therethrough, and a plurality of axially extending bores 13 extending through the housing parallel to and disposed around said central aperture 12. A rodshaped permanent magnet 14 is disposed in each of said bores with the like poles of said magnets at the same ends of said housing member 11. End plates, or cover plates, 17 and 18 of magnetic material are positioned over the opposite ends of housing member 11, and extend radially over the ends of permanent magnets 14.

Coaxial line connectors, .or terminals, 21, 22 and 23 extend through the sides of housing member 11 and the center conductors 21, 22 and 23' of said connectors are conductively connected to a conductive disc 25 that is centrally positioned within aperture 12. A strip transmission line junction thus is formed wherein conductive disc 25 is the center conductor and the inner surfaces of end members 17 and 18 form the respective ground planes of said junction. Preferably, at least the inner surfaces of end members 17 and 18 are of a good conductive material to assure low attenuation of waves propagating through the junction. I

Two discs, or posts, 27 and 28 of magnetically polarizable material which exhibits gyromagnetic properties at the frequencies of interest are axially disposed within the junction on opposite sides of central conductive disc 25. The material of discs 27 and 28 may be ferrite, garnet, or other known material capable of exhibiting the desired properties. These materials are well known and are commercially available. A yttrium-aluminum-iron garnet, whose properties will he set forth more fully below, has been used with success to achieve diplexing operation in a device of the type illustrated in FIGS. 1 and 2.

As may be seen by the dashed lines in FIG. 2, a mag netic circuit for biasing gyromagnetic elements 27 and 28 is established from the north poles of permanent magnets 14, centrally through the top end member 17, axially through members 27 and 28 of gyromagnetic material'and radially through bottom end member 18 to the south poles of permanent magnets 14. It thus may be seen that the devices of FIGS. 1 and 2 have the physical form of a symmetrical Y-junction circulator.

In the operation of the device of FIGS. 1 and 2 to di plex electromagnetic waves of two diiferent frequencies f and f the properties of the gyromagnetic material of gyromagnetic members 27 and 28', the strength and direction of the unidirectional magnetic field supplied by permanent magnets 14 and the two frequencies f and f \are chosen with respect to each other, as will be more fully explained below,. so that when electromagnetic waves at the two frequencies f and f are both coupled into the junction at terminal 23', FIG. 3, electromagnetic waves at frequency f will be circulated in one direction substantially exclusively to terminal 21 and electromagnetic waves at frequency f will be circulated in the op posite directionsubstantially exclusively to terminal 22, thus separating the electromagnetic waves at the two fre quencies and achieving the desired diplexing operation.

With the direction of magnetic field remaining in the same direction as for the operation just described, the device will not inherently operate to diplex in the opposite direction. That is, electromagnetic waves at frequencies f and f coupled respectively into terminals 21 and 22 will not propagate through the junction to terminal 23. Waves at frequency f coupled into terminal 21 will be circulated substantially exclusively to terminal 22, and waves at frequency coupled into terminal 22 will be circulated substantially exclusively to terminal 21.

The device of this invention may be operated to combine at terminal 23 waves at frequencies f and f coupled into the junction respectively at terminals 21 and 22 \by reversing the direction of the unidirectional magnetic field which magnetizes gyrornagnetic members 27 and 28. This mode of operation is illustrated in FIG. 4 wherein the direction of the magnetizing field is illustrated 'by the encircled cross that represents the tail of a magnetic field vector. The direction of this magnetic field vector is opposite to the direction of the magnetic field vector in FIG. 3 wherein the encircleddot represents the head of the magnetic field vector. With all other conditions remaining the same, the direction of circulation of the two frequencies in the device illustrated in FIG. 4 will be reversed from that illustrated in FIG. 3 and the electromagnetic waves at frequencies f and f coupled respectively into terminals 21 and 22 will be circulated in opposite directions through the junction and both will couple from out put terminal 23.

The means and procedure for obtaining the correct operating characteristics of the device of this invention now will be described. Diplexing operation with the device of this invention was achieved after first realizing that frequencies below the gyromagnetic resonance frequency of the magnetized gyromagnetic material were circulated in one direction through a symmetrical Y-junction circulator and that frequencies above resonance were circulated in the opposite direction through such a device. It was found, however, that standard commercial Y-junctiou circulators would not perform the desired diplexing action because the conditions and characteristics necessary for optimum circulating operation at one frequency were not the proper conditions and characteristics for circulation in the opposite direction at any other frequency. Diplexing operation was achieved by determining what characteristics of a gyromagnetic material and what strength of unidirectional magnetic field were required to diplex two different frequencies. These characteristics and conditions may be determined in the following manner. Referring to FIGS. 5 and 6, a group of diiferent gyromagnetic materials a through 1 are selected, the different materials having different saturation magnetizations (41rMs). The different materials are individually placed in the device of FIGS. 1 and 2, and the magnetic field strength and frequency of the electromagnetic waves are varied to determine =both the frequency for optimum operation for a frequency below resonance (circulation in a first direction) and the frequency of optimum operation for a frequency above resonance (circulation in the opposite direction). The two curves of FIG. 5 represent the frequencies for optimum operation above and below resonance for the materials a through 1 Whose saturation magnetizations vary from approximately 320 to approximately 1450 gauss. In FIG. 6, the field strengths of the unidirectional magnetic field required to obtain optimum operation at the frequencies indicated in FIG. 5 are plotted against the saturation magnetizations of the materials a through 1. It may be seen that at a magnetic field strength of approximately 1500 gauss the material a having a saturation magnetization of approximately 320 gauss will produce optimum circulation of two differentfrequencies in opposite directions. In FIG. 5, the frequencies above and below resonance associated with material a are approximately 7.4 kmc. and 5.5 lcmc, respectively. Material a is a yttrium-iron-aluminum garnet having the following composition: 3Y O .5(25% Al O .75% Fe O This material has a linewidth of approximately 38 oersteds.

The present invention is not limited to use in strip transmission line devices, but is equally useful in hollow waveguide types of circulators as well. Also, the practice of the invention is not limited to a symmetrical Y-junction circulator, but may be used in other types of common junction devices such as a T-junction, or other arrangements of the star junction variety.

While the invention has been described in its preferred embodiments, it is to be understood that the words which have been used are words of description rather than of limitation and that changes within the purview of the appended claims may be made without departing from the true scope and spirit of the invention in its broader aspects.

What is claimed is:

1. Apparatus for diplexing electromagnetic waves at first and second different frequencies comprising,

a plurality of electromagnetic wave transmission lines lying in a common plane and joined in a common junction,

means for coupling electromagnetic waves at said first and second frequencies to said junction,

a magnetically polarizahle material capable of exhibiting gyromagnetic properties at said first and second frequencies disposed within said common junction,

at source of unidirectional magnetic flux for magnetizing said gyro-magnetic material to a state of magnetization so that the gyromagnetic resonance frequency of the magnetized material is intermediate said first and second frequencies,

the field strength of said magnetic flux being proportioned with respect to said first and second frequencies and the characteristics of said gyromagnetic material to cause said electromagnetic waves at said two frequencies to couple from first and second ones of said transmission lines through said junction and substantially exclusively to a third one of said transmission lines when said magnetic flux is directed in a first direction and to cause said electromagnetic waves at said two frequencies to couple from one of said transmission lines through said junction and substantially exclusively to respective ones of said transmission lines when said magnetic flux is directed in an opposite direction.

2. Apparatus for diplexing electromagnetic waves at first and second different frequencies comprising,

a plurality of electromagnetic wave transmission lines lying in a common plane and joined in a common unction,

means for coupling electromagnetic waves at said first and second frequencies to a first one of said transmission linm for the propagation of the electromagnetic waves at said two frequencies through said junction,

a magnetically polarizable material that exhibits gyromagnetic properties at said first and second frequencies disposed within said common junction,

:1 source of unidirectional magnetic flux for magnetizing said gyromagnetic material to a state of magnetization at which the gyromagnetic resonance frequency of the magnetized material is intermediate said first and second frequencies,

the field strength and direction of said magnetic flux and said first and second frequencies and the characteristics of said gyromagnetic material being so proportioned that electromagnetic waves at said first and second frequencies propagate through said junction in opposite directions and waves at said first frequency couple substantially exclusively to a second one of said transmission lines and electromagnetic waves at said second frequency couple substantially exclusively to a third one of said transmission lines.

3. A diplexer for separating electromagnetic waves at first and second idiiferent frequencies comprising,

a plurality of electromagnetic wave transmission lines lying in a common plane and joined in a common junction, at magnetized magnetically pol arizable material that exhibits gyromagnetic resonance to electromagnetic waves at a given frequency disposed within said common junction,

Ia first source of electromagnetic waves at a first frequency that is lower than the gyromagnetic resonance frequency of said magnetized gyromagnetic material coupled to the input of a first one of said transmission lines,

a second source of electromagnetic waves at a second frequency that is higher than the gyromagnetic resonance frequency of said magnetized gyromagnetic material coupled to the input of a second one of said transmission lines,

an output terminal coupled to a third one of said trans mission lines and adapted to receive electromagnetic I References Cited in the file of this patent Waves at said first and second frequencies, UNITED STATES PATENTS the magnetization and the characteristics of said gyromagnetic material and the first and second frequencies 2954535 Porter Sept 1960 of the electromagnetic Waves from said two sources 5 OTHER REFERENCES being proportioned to cause the electromagnetic A Y-Junct-ion Strip-Line Ciroulator, Milano et ah, Waves from Said two sources to Propagate through IRE Transactions on Microwave Theory and Techniques, said junction in opposite directions and to be coupled May 1960, pages 346-35. substantially exclusively to said output terminal of New Microwave Circulators, C-heit et al., Electronics,

the third transmission line. 10 December 18, 1959, pages 81-83. 

1. APPARATUS FOR DIPLEXING ELECTROMAGNETIC WAVES AT FIRST AND SECOND DIFFERENT FREQUENCIES COMPRISING, A PLURALITY OF ELECTROMAGNETIC WAVE TRANSMISSION LINES LYING IN A COMMON PLANE AND JOINED IN A COMMON JUNCTION, MEANS FOR COUPLING ELECTROMAGNETIC WAVES AT SAID FIRST AND SECOND FREQUENCIES TO SAID JUNCTION, A MAGNETICALLY POLARIZABLE MATERIAL CAPABLE OF EXHIBITING GYROMAGNETIC PROPERTIES AT SAID FIRST AND SECOND FREQUENCIES DISPOSED WITHIN SAID COMMON JUNCTION, A SOURCE OF UNIDIRECTIONAL MAGNETIC FLUX FOR MAGNETIZING SAID GYROMAGNETIC MATERIAL TO A STATE OF MAGNETIZATION SO THAT THE GYROMAGNETIC RESONANCE FREQUENCY OF THE MAGNETIZED MATERIAL IN INTERMEDIATE SAID FIRST AND SECOND FREQUENCIES, THE FIELD STRENGTH OF SAID MAGNETIC FLUX BEING PROPORTIONED WITH RESPECT TO SAID FIRST AND SECOND FREQUENCIES AND THE CHARACTERISTICS OF SAID GYROMAGNETIC MATERIAL TO CAUSE SAID ELECTROMAGNETIC WAVES AT SAID TWO FREQUENCIES TO COUPLE FROM FIRST AND SECOND ONES OF SAID TRANSMISSION LINES THROUGH SAID JUNCTION AND SUBSTANTIALLY EXCLUSIVELY TO A THIRD ONE OF SAID TRANSMISSION LINES WHEN SAID MAGNETIC FLUX IS DIRECTED IN A FIRST DIRECTION AND TO CAUSE SAID ELECTROMAGNETIC WAVES AT SAID TWO FREQUENCIES TO COUPLE FROM ONE OF SAID TRANSMISSION LINES THROUGH SAID JUNCTION AND SUBSTANTIALLY EXCLUSIVELY TO RESPECTIVE ONES OF SAID TRANSMISSION LINES WHEN SAID MAGNETIC FLUX IS DIRECTED IN AN OPPOSITE DIRECTION. 